Clamp



Feb 2?, 1951 H. THOMASON 2,543,387

CLAMP Original Filed June 50, 1941 In 1m, 4 m. INVENTOR 38 36 39 him/mar Tfiamason @Y ZA n/ ATTORNEY Patented Feb. 27, 1951 NITED STATES ATENT OFFICE 501,358, September 6, 1 March 13, 1948, Serial 9 Claims. (CL 51217) This invention relates to a clamp structure and, more particularly, to one adapted to be used to hold a brake shoe during the process of grinding.

This application is a division of an application filed on June 30, 1941, in the name of Hjalmar Thomason, under Serial Number 400,417, which issued as Patent No. 2,345,161, dated March 28, 1944 and entitled Brake Shoe Grinder. It is also a continuation of application Serial NumberfiOL-SSS, filed on September 6, 1943, now abandoned.

Brake shoe linings should "be ground so that the brake shoes may properly contact the brake drums. During the process of grinding, a substantial stress is exerted upon the brake shoe. Accordingly, the shoe should be strongly clamped so as to withstand these stresses.

It is one of the objectsof this invention to make it possible to clamp the brake shoe to :be

operated upon in an effective and :simplemanher.

It is another objectof thisinvention -to.provide a clamp that may easily .beaccommodated to suit brake shoes having radii falling Within wide limits.

It is still another object of this invention to make it possible to accommodate in an effective manner a variet of sizes of shoes.

One difiiculty that often arises is'thatafirrn grip upon the shoe for holding it against .the grinding surface may cause the shoe to besprung from its normal unstressed position; and, after the grinding operation is performed and .the grip relaxed, the grinding surface departsfrom the true cylindrical form desired. It-is another object of this invention to make it possible to clamp the shoe firmly withoutspringing or warping it.

Brake shoes provided for modern automobiles are manufactured from structural iron sections by either the rolling or pressing process. -This method of manufacture, While economical, does not produce a shoe that isaccurate in size; nor can it produce a brake shoe in which all of the parts are perfectly formed.

Accordingly, in orderthat-thebrake shoe lining may accuratelyfit the drum, it=is necessary to grind the brake lining after-it has been'applied on the shoe. Whenthe brake shoe-is-first manufactured for installation as a piece of equipment in a new car, the problem of-making a fixture-for hold-ing the shoe-whilegrinding-is a relatively simple one. fIhe-shoemay-be located in the fixture at the point at which it isanchored Continuation of application Serial No. 943. This application No. 14,801

to the brake mechanism, a special fixture being made, as'a rule, for each size and style of brake shoe.

For obvious reasons, this type of fixture is not practical in the automotive service field, where innumerable styles and sizes of brake shoes, ranging back for fifteen or more years, have to be serviced. A fixture for this type of Work must of necessity be universal, so as to accommodate brake .shoes of various styles and sizes. In order to be practical, it must locate the shoe in the fixture in such a way that it is not only held accurately on the center of the are on which it is ground, but also squarely to permit the full Width of the face of the lining to contact the braking surface of the drum. The shoe must be held in such manner that no stresses are put on it While the grinding operation is performed. Usually, brake shoe grinders of the prior art are provided with shoe holding fixtures that hold the shoe by its central web or flange. Accordingly, in such fixtures reliance must be placed upon the trueness of the central web with respect to the face of the shoe, It is readily understood that the center web of a brake shoe made by the forming or rolling process cannot, even when new, always be in perfect alignment with the face of the shoe. There are, furthermore, brake shoes, such as are used by Lockheed hydraulic brakes, in which the center web has a taper. This taper would naturally throw the face of the shoe out of alignment when it was placed fiat on the web and held in such a position while grinding. It is also a well known fact that the modern brake shoe,'being of light construction, often becomes deformed in service, changing in size and becoming twisted.

.It is another object of this invention to provide a, fixture for holding a brake shoe, or the like, andwhich is readily adjustable, so as to accommodate brake shoes of various sizes, and having contact points above and below the center Web to hold a brake shoe in perfect alignment with respect to the grinding surface. .An additional objectof this invention is to provide a means whereby -a twisted brake shoe may be aligned from its, centerin such a manner as to minimize the effect of the twist.

This invention possesses many other advantages, and has other objects Which may be made more clearly apparent from a consideration of one embodiment .of the invention. For this purpose-there is shown a form in the drawings accompanying' and forming part of the present specification. The. form willnow be describedindm .5 tall, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of this invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a transverse section of a. clamp structure, incorporating the invention and parts of a grinder associated therewith, and shown holding a brake shoe;

Fig. 2 is a top plan view of the clamp structure, shown as in use, for holding a brake shoe having imperfect alignment;

Fig. 3 is a view taken substantially from the plane 33 of Fig. 2;

Fig. 4 is a detail sectional view, taken along plane 5-4 of Fig. 2; and

Fig. 5 is a diagram illustrating the possible points of contact between the clamp and the concave side of the brake shoe.

In the present instance there is shown an arcuate brake shoe i that has a central flange or web 2 extending away from the concave side of the shoe Brake shoe lining 3, carried on the convex side of shoe i, is adapted to be ground by the aid of an abrasive wheel 3 (Figs. 1 and 2). This abrasive wheel is shown as having a vertical axis 5 about which the wheel 1 rotates.

As described in the parent application, the brake shoe 5 is so mounted and supported by a clamp structure that it may be moved about an axis 5 parallel with the axis 5. The distance between the parallel axes and 6 may be set by ap propriate i echanism, all as described in the said parent application. This setting is made to conform to the desired radius of curvature of the ground surface of lining 3. Furthermore, by other appropriate mechanism, indicated generally by the reference character '1', the brake shoe i may be fed toward the abrasive wheel 6, while the distance between the axes 5 and 6 is maintained fixed. Since this mechanism is shown and described in detail in the parent application, further description thereof is unnecessary.

The clamp includes a supporting bar 8 that has a longitudinal direction of movement transverse to axes 5 and 6. This movement may be gradual, to cause the lining 3 to be fed to the wheel 4.

At its right-hand end the bar 8 is provided with a slot 9 into which the web or flange 2 of the brake shoe i may extend.

The remainder of the clam structure I is adjustably mounted upon the bar 8. For this purpose there is a hub ii through which the bar 8 extends. This hub i i may be held in any adjusted position with respect to the bar 8 by the aid of a set screw l2. This set screw i2 is threadedly engaged in a boss formed on the hub ii, and is also provided with a handle i l. The lower end of the screw 52 engages a flattened surface I (Fig. 2) that is formed on the top of the bar 8, which is otherwise cylindrical. From the hub Ii an upper and a lower set of arms project. The lower set of arms l6 and i1 (Figs. 2, 3, and 4) are provided respectively with pins l8 and E?) that project upwardly into contact with the lower surface of web flange 2. These pins are shown as having fiat upper surfaces.

Cooperating to clamp the flange or web 2 against the pins |3-|9 are a pair of pins 2D-2i with rounded ends. These pins extend through clearance apertures in the upper set of arms 22 and 23 that are formed integrally with hub H.

These pins 25 and 2| are urged downwardly against the upper surface of flange or web 2.

For this purpose they are carried by the arms 24 and 25 of a frog 26. This frog 2% is arranged to be urged downwardly about a fulcrum provided by the lower end of adjustable screw 2'! for urging pins 26-2i' against the web 2. Screw 2! is conveniently threaded through the left-hand portion of the frog 26 and rests upon a surface 28 formed on hub H.

For urging the frog 26 downwardly to clamp the web 2, there is provided a screw 29 threaded into boss 30 of hub H. This screw 29 passes through clearance apertures 3| in the frog 23, and its upper end is engaged by a hand nut 32. This hand nut 32 is manipulable by handle 33. The nut 32 is arranged to contact the upper surface of a boss 3 formed on the frog 26.

Turning of the handle 33 in the proper direction thus urges the frog 26 in a clockwise or clamping direction about the fulcrum formed between the screw 21 and surface 28.

The set screw |2 also passes through a clearance aperture in the frog 26. Furthermore, a compression spring 35 may be utilized between boss 34 and the lower surface 01' the frog to lift this frog when the nut 32 is released.

In order to maintain the face of brake shoe in alignment for grinding, the concave surface of this brake shoe is contacted at several points of the clamp structure. Thus, the bar 8 carries at its right-hand end the pair of pins 36 and 3?, shown most clearly in Fig. 3. These extend on opposite sides of the web or flange 2, and are arranged to be placed in contact with the concave surface of shoe In order further to contact the brake shoe I, each of the arms l6, I1, 22, and 23 is further provided with contacting areas or points designated by reference characters 38, 39, 4D, and 4| respectively. The pair of contacting points 38 and 40 are arranged on opposite sides of the web or flange 2; and the same is true of the contacting surfaces 39 and 4|.

The clamping structure is purposely so constructed that it may readily accommodate itself to the irregularities encountered in brake shoes. For example, in urging pins 20 and 2| downwardly to clamp the web 2, the rounded lower surfaces of these pins may accommodate themselves to the upper surface of the web 2, because the fulcrum formed between the screw 21 and the surface 28 is not fixed; and the frog 26 can move longitudinally and laterally to permit pins 2| to accommodate themselves to the web 2. Since screws l2 and 3| pass through apertures in the frog that have substantial clearance, accommodation of the frog to the web 2 in this manner is readily permitted.

In setting up a brake shoe l for grinding, the screw I2 is loosened. The web 2 is passed between the pins |8-20 and |9-2|. The brake shoe 2 is inserted far enough so that as many of the surfaces 38, 39, 46, and 4| as is possible are in simultaneous contact with the concave side of the brake shoe I. These surfaces, together with pins 36, 31, are diagrammatically illustrated in Fig. 5. The screw 29 may be tightened to clamp the web 2 after these surfaces are placed in contact with the shoe. Then the bar 8 is advanced toward the right until it is stopped by the engagement of pins 36, 31 against the concave surface of the brake shoe Screw I2 is then tightened.

The clamp is now in condition to hold the brake shoe during the grinding operation.

As heretofore stated, due to the mode of manufacture of the brake shoes, the arcuate-configuration may depart slightly from a true circle. The Web or flange 2 may be also slightly warped; and the face of the shoe may be out of parallelism with the grinding surface. For this reason, it is probable that not all of the surfaces 38, 39, 49,

and ii and those at the ends of pins 36-3'I, may be in simultaneous contact with the concave side of the brake shoe I. For example, the surface H is shown as out of contact with the face of shoe I (Figs. 2 and 4), the face being slightly misaligned and inclined to the vertical. The lining 3, however, has been ground true by wheel 4.

The brake shoe is nevertheless contacted by some surfaces above the web or flange 2, and by some below the web or flange 2. Thus, the shoe i will be maintained in perfect alignment for grinding. Furthermore, it is possible, by slight angular adjustment of the brake shoe I, to find a position where substantially all of the surfaces will be in good contact with the concave side of shoe I. Such an adjustment can be made While the clamp nut 32 is loosened, permitting the operator to move the brake shoe I between the pins IB20 and I9ZI. Such angular movement is indicated by the dot-ancl-dash lines in Figs. 2 and 5. After an improved position is found, the clamp may be re-applied by tightening the screw 32.

The set screw I2 being tightened, the relative position of hub I I and bar8 (defining the position of pins 36 and'B'I) corresponds to a definite radius of the brake shoe I. This adjustment need not be altered while brake shoes of the same size are being ground. To adjust the clamp to another size, it is merely necessary to loosen the set screw I2 and to readjust the position of the bar 8 with respect to the clamp frog 26.

By the aid of the supporting or bracing surfaces illustrated in Fig. 5, the brake shoe I is adequately supported in an aligned position. This, coupled with the relative freedom of movement of frog'25 to permit accommodation of the clamp to irregular webs or flanges 2, makes it possible to grind the brake shoe lining 3 in an accurate manner. No undesired strain are produced by the clamp on the brake shoe I. The supporting surfaces are adequate to withstand the strain imposed upon the brake shoe during the grinding operation.

The inventor claims:

1. In a structure for firmly supporting a brake shoe While a machining operation is performed thereon, said brake shoe having an arcuate face: means forming a pair of supporting surfaces of limited extent upon which the shoe can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; means having corresponding limited surfaces directly opposed to the supporting surfaces respectively and contacting the shoe to clamp the shoe against the said supporting surfaces by exertion of a force generally parallel to the axis of the arcuate face; and means forming a pair of abutments of limited areas against which the concave side of the shoe ma rest, said abutments being spaced in a direction parallel to the axis of the face and angularly spaced between said supporting surfaces, said abutments being on opposite sides of the supporting surfaces to assist in sustaining a thrust imposed by the machining operation in a direction toward said center.

2. In a structure for firmly supporting a brake shoe While a machine operation is performed thereon, .said brake shoe having an I arcuate race with a rear concave surfacean'cl aflange extending fromsaid surface andintermediate the oppositeedges thereof; means forminga pair of supporting surfaces'of limited extentupon which one side of the flange can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; means having corresponding limited surfaces directly opposed to the supporting surfaces respectively and contacting the other side of the flange for clamping the flange against the said supporting surfaces by exertion of a force generally parallel to the axis of the arcuate face; and means for positioning the shoe with respect to said supporting and clamping means, said positioning means providing limited surfaces adapted to contact the concave surface of the shoe and on opposite sides of the supporting surfaces, said positioning surfaces being angularly spaced. with respect to the center of the arcuate face.

3. In a structure for firmly supporting a brake shoe while a machine operation is performed thereon, said brake shoe having an arcuate face with a rear concave surface and a flange extending from said surface and intermediate the opposite edges thereof; means forming a pair of supporting surfaces of limited extent upon which one side of the flange can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; means having corresponding limited surfaces directly opposed to the supporting surfaces respectively and contacting the other side of the flange for clamping the flange against the said supporting surfaces by exertion of a force generally parallel to the axis of the arcuate face; 'means for positioning the shoe with respect to'said supporting and clamping means, said positioning means providing limited surfaces adapted to contact the concave surface of the shoe and on opposite sides of the supporting surfaces, said positioning surfaces being angularly spaced with respect to the center of the arcuate face; and means for assisting to sustain the thrust imposed by the machining operation in a direction toward said axis, comprising a member baving'a pair of surfaces of limited extent capable of being placed in contact with the concave side of the shoeand on opposite sides of the supporting surfaces, and intermediate the positioning surfaces.

4. In a structure for firmly supporting a brake shoe while a machine operation is performing thereon, said brake shoe having an arcuate face with a rear concave surface and a flange extending from said surface and intermediate the opposite edges thereof: means forming a pair of supporting surfaces of limited extent upon which one side of the flange can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; means having corresponding limited surfaces directly opposed to the supporting surfaces respectively and contacting the other side of the flange for clamping the flange against the said supporting surfaces by exertion of a force generally parallel to the axis of the arcuate face; means for positioning the shoe with respect to said supporting and clamping means, said positioning means providing limited surfaces adapted to contact the concave surface of the shoe and on opposite sides of the supporting surfaces, said positioning surfaces being angularly spaced with respect to the center of the arcuate face; and means for assisting to sustain the thrust imposed by the machining operation in a direction toward said axis, comprising a member having a pair of surfaces of limited extent capable of being placed in contact with the concave side of the shoe and on opposite sides of the supporting surfaces, and intermediat the positioning surfaces; and means in which said member is adjustable in a generally radial direction with respect to the arcuate face, for ensuring contact between said member and the concave face for different radii of the concave face.

5. In a structure for firmly supporting a brake shoe while a machining operation is performed thereon, said shoe having an arcuate face: means forming a pair of supporting surfaces of limited extent upon which the shoe can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; means movable to clamp the shoe against said surfaces, said means having limited areas of contact; and means restricting the movement of said clamping means at all times so that the said areas of contact extend directly opposite the supporting areas.

6. In a structure for firmly supporting a brake shoe while a machining operation is performed thereon, said shoe having an arcuate face: means forming a pair of supporting surfaces of limited extent upon which the shoe can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; and means having limiteu surfaces directly opposed to the supporting surfaces respectively, and contacting the shoe to clamp the shoe against the said supportin surfaces; and means forming abutting surfaces for the concave side of the shoe, at least one abutting surface being below the supporting surfaces and angularly spaced therefrom, and at least another abutting surface being above the supporting surfaces and angularly spaced from the other abutting surface.

7. In a structure for firmly supporting a brake shoe while a machining operation is performed thereon, said shoe having an arcuate face: means forming a pair of supporting surfaces of limited extent upon which the shoe can rest, the surfaces being spaced apart by a substantial angular distance from each other in respect to the center of the circular arcuate face; and means having limited surfaces directly opposed to the supporting surfaces respectively, and contacting the shOe to clamp the shoe against the said supporting surfaces; and means forming abutting surfaces for the concave side of the shoe, said abutting surfaces being arranged in pairs, one of each pair being above the supporting surfaces and the other of the pair being below the supportin surfaces.

8. In a brake shoe clamp: a member having spaced arms between which the flange of a brake shoe may project; a pair of spaced means carried by one of the arms and providing supporting surfaces of limited extent for the flange; the other of said arms having apertures opposite said supporting surfaces; and clamping means extending through said apertures and having surfaces directly opposed to the supporting surfaces.

9. In a brake shoe clamp: a member having spaced arms between Which the fiange of a brake shoe may project; a pair of spaced means carried by one of the arms and providing supporting surfaces of limited extent for the flange; the other of said arms having apertures opposite said supporting surfaces; said arms having surfaces for contacting the concave side of the shoe; and clamping means extending through said apertures and having surfaces directly opposed to the supporting surfaces.

I-IJALMAR THOMASON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,453,737 Williams May 1, 1923 1,625,049 Oliver Apr. 19, 1927 2,102,915 Rishel Dec. 21, 1937 2,246,290 Broxon June 17, 1941 2,289,693 Blazek July 14, 1942 2,304,530 Bigelow Dec. 8, 1942 2,325,826 Barrett Aug. 3, 1943 2,328,650 Johnson et a1 Sept. 7, 1943 2,345,161 Thomason Mar. 28, 1944 FOREIGN PATENTS Number Country Date 161,436 Germany July 7, 1905 

